Generally, a cleaning agent bottle has a pressable head at a top of the bottle for discharging liquid from the container. Thus it is unnecessary to open or close a cover in use and the user can obtain the cleaning agent by pressing the head.
In one prior art device, a pressable head is assembled in an opening of a container. An inner tube of the pressable head can be driven downwardly by pressing of the head. At the bottom of the inner tube, there is a plug and an elastic element. When the inner tube is pressed, the liquid in the container will be sucked out from the container. When the head is released, the head will return to it's original position by the resilient force of the elastic element so as to suck the liquid in the container repeatedly.
However, although the prior art structure has the effect of sucking liquid in the container, when the material in the container is not a clear liquid, such as one containing particles or emulsion, they will create wear of the inner wall of the retaining tube. As a result, gaps are formed and thus the pumping effect obtained by pressing the head is reduced. As a whole, the prior art structure is not a prefect one and needs to be improved.